Parasitic trematodes e.g., Schistosoma mansoni and Fasciola hepatica are helminth parasites that infect hundreds of millions of humans and livestock worldwide. Schistosomes alone in 1977-78 were estimated to infect about 350 million people, 1 million of whom died. Curiously, the pathobiology of these parasites is more a result of their egg production than any inherent behavior of the adult. Entrapped masses of eggs cause inflammation and fibrosis of surrounding tissues. This proposal is concerned with the biochemistry of eggshell formation in F. hepatica and S. mansoni. The long range goal is to prevent proper eggshell formation in these parasites. The immediate goals are (1) to isolate and characterize the eggshell precursor protein and sequence its dopa-containing domains, (2) isolate the eggshell cross-linking enzyme, tyrosinase, and characterize its kinetics and physical properties, and (3) to prepare antibodies to these two proteins so that they can be immunofluorescently localized in the vitellocytes as well as in nascent eggshell.